Selby remains on course for back-to-back crowns after booking a quarter-final place with a convincing 13-6 win over Xiao Guodong.
The pre-tournament favourite, who led 10-6 overnight, began Monday's session in blistering style, winning three successive frames to quickly dispose of his Chinese opponent.
Selby, Crucible winner in 2014 and 2016, produced a century (101) in the opening frame of the session - his only one in the match - and then cleared up with a break of 73 to take the second after Xiao twice let him back in.
World number 44 Xiao had given himself hope in the match by winning the final two frames on Sunday but he failed to recapture that form as Selby sealed a comfortable passage into the next round with a break of 60.
"I felt as though I played a really solid game and didn't really make too many mistakes. I put Xiao under pressure and a lot of the time when he missed I seemed to capitalise. Coming into this session with a four-frame lead was vital," Selby said.
"Xiao is a great player. He got to the final at the Shanghai Masters a few years ago and I thought he was going to kick on. He didn't really and sort of hit a brick wall for a couple of seasons. He's proved again this tournament what a great player he is and he has a good future.
"I don't feel under pressure as much, but I suppose that goes down to the season I've had leading into it.
"If I'd come here having not won anything and struggling a bit for form it would have been a little bit different with the defending champion tag on my back. But that isn't the case this year and I seem to be really relaxed and enjoying my snooker and I think it is showing."
The world number one will next face Marco Fu, who won a thrilling last-16 meeting with Neil Robertson.
Fu's 13-11 victory was full of drama as Robertson, a winner at the Crucible in 2010, missed on the black to take the contest to a deciding 25th frame.
The pair were locked at 10-10 at the interval before Robertson potted the black-ball decider in the next frame to go ahead, shouting, 'Come on' and beating the table in a rare show of emotion.
Fu responded by nudging back ahead and he looked to be cruising when up 57-0 in the penultimate frame but a kick on a routine red handed the initiative back to Robertson, who failed to take advantage when left with a long shot on the black that he could not sink, while his opponent did.
On the other table, former finalist Barry Hawkins set up a last-eight meeting with Stephen Maguire by overcoming 2006 champion Graeme Dott.
World number seven Hawkins, who lost the 2013 final to Ronnie O'Sullivan, was three frames from victory when play restarted and he made light work of Dott to complete a 13-6 success.
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